chore(dev): fix span duration in tests

[vigneshshanmugam]

• Our unit tests for the latest server snapshot started breaking because of the new changes in Server which disallows spans with negative duration docs/spec: require duration >= 0 apm-server#3721. This PR fixes the span with correct duration.

[hmdhk]

@vigneshshanmugam , Let's merge once tests are green.

[codecov-io]

Codecov Report

Merging #778 into master will increase coverage by 2.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #778      +/-   ##
==========================================
+ Coverage   92.20%   94.33%   +2.12%     
==========================================
  Files          50       49       -1     
  Lines        2694     2171     -523     
  Branches      579      426     -153     
==========================================
- Hits         2484     2048     -436     
+ Misses        207      120      -87     
  Partials        3        3              

Impacted Files	Coverage Δ
packages/rum-core/src/common/apm-server.js	79.69% <0.00%> (-4.67%)	⬇️
packages/rum-core/src/common/service-factory.js	89.18% <0.00%> (-3.41%)	⬇️
packages/rum-core/src/common/utils.js	94.30% <0.00%> (-0.75%)	⬇️
packages/rum-core/src/index.js	100.00% <0.00%> (ø)
packages/rum-core/src/common/context.js	100.00% <0.00%> (ø)
packages/rum-core/src/common/constants.js	100.00% <0.00%> (ø)
packages/rum-core/src/error-logging/index.js	100.00% <0.00%> (ø)
...kages/rum-core/src/performance-monitoring/index.js	100.00% <0.00%> (ø)
...e/src/performance-monitoring/capture-navigation.js	100.00% <0.00%> (ø)
packages/rum-core/src/common/compress.js
... and 3 more

[ghost]

💚 Build Succeeded

Expand to view the summary

Build stats

• Build Cause: [Pull request chore(dev): fix span duration in tests #778 opened]

• Start Time: 2020-05-04T11:32:05.798+0000

• Duration: 87 min 20 sec (5240364)

• Commit: 12015e3

Test stats 🧪

Test	Results
Failed	0
Passed	892
Skipped	8
Total	900

Steps errors

Expand to view the steps failures

• Name: Bundlesize

  • Description: #!/bin/bash set -o pipefail npm run bundlesize|tee bundlesize.txt

  • Result: FAILURE

  • Duration: 1 min 32 sec<

  • Start Time: 2020-05-04T11:37:18.104+0000

• Name: Start Elastic Stack 7.6.0 - @elastic/apm-rum-angular - none

  • Description:

  • Result: FAILURE

  • Duration: 4 min 6 sec<

  • Start Time: 2020-05-04T11:45:06.184+0000

• Name: Start Elastic Stack 8.0.0-SNAPSHOT - @elastic/apm-rum-vue - none

  • Description:

  • Result: FAILURE

  • Duration: 4 min 43 sec<

  • Start Time: 2020-05-04T11:45:31.128+0000

• Name: Error signal

  • Description:

  • Result: FAILURE

  • Duration: 0 min 0 sec<

  • Start Time: 2020-05-04T12:39:00.522+0000